Installation for utilizing surplus heat from a power transformer

ABSTRACT

The invention relates to an installation for utilizing surplus heat from a power transformer. A first pipe system ( 7 ) is connected to the cooling device of the transformer for circulation of a first, heat carrying fluid between the transformer and a heat pump ( 5 ) with the purpose of enabling emission of heat to an evaporator ( 10 ) included in the heat pump, which evaporator via a second pipe system ( 11 ) containing a second fluid communicates with a compressor ( 12 ), a condenser ( 13 ) and an expansion valve ( 14 ), a third pipe system ( 15 ) having a third, heat carrying fluid for transfer of heat to one or more consumption units ( 16 ) being connected to the condenser. A fourth pipe system ( 19 ) is directly or indirectly connected to the first pipe system ( 7 ), which is partly brought down in a combined heat accumulator and emitter ( 20 ) in rock, ground and/or water, a multi-port valve ( 23 ) acting between the first and fourth pipe systems ( 7, 19 ) for enabling leading of surplus heat from the transformer via the first pipe system to either the evaporator ( 10 ) of the heat pump or said heat accumulator or emitter ( 20 ).

BACKGROUND OF THE INVENTION

[0001] In the windings of power transformers, heat is generated whichhas to be evacuated from the transformer and the immediate vicinitythereof. In small transformers, this is usually carried out byair-cooling via cooling flanges, while larger transformers are cooled bymeans of oil, e.g. by circulating oil, such as mineral oil, through thewindings of the transformer and ducts in the core thereof, oralternatively by the fact that the core and the windings are immersed inan oil bath in an outer container. Irrespective of which type of coolingdevice being used, the heat evacuation constitutes a waste of energy, aswell as a practical and economic problem so far that inefficient coolingand high temperatures results in premature deterioration of thetransformer and the equipment in connection thereto. A particularproblem consists of instantaneous or seasonal temperature variations inthe outdoor air in asmuch as high outdoor temperatures impairs or makesthe cooling more difficult. Furthermore, temperature variations arise asa consequence of varying power-extraction from the transformer.

OBJECTS AND FEATURES OF THE INVENTION

[0002] The present invention aims at obviating the above-mentionedproblems by providing an installation by means of which the surplusenergy from power transformers may be utilized in an economically usefulway at the same time as the transformer may be cooled in an efficientway independent of seasonal or other variations in outdoor temperature.Thus, a primary object of the invention is to provide an energyutilization installation which, if required, enables direction of thesurplus heat energy from a power transformer, either entirely or partly,to heat consumption units, such as radiators in dwelling-houses or otherbuildings, or entirely or partly to a heat accumulator. An additionalobject is to provide an installation suitable for the purpose, which isstructurally simple and may be produced in an inexpensive way, in themain by the use of commercially available standard components.

[0003] According to the invention, at least the primary object isattained by the features defined in the characterizing clause ofclaim 1. Preferred embodiments of the installation according to theinvention are furthermore defined in the dependent claims.

BRIEF DESCRIPTION OF THE APPENDED DRAWING

[0004] In the drawing:

[0005]FIG. 1 is a planar view of a transformer house, in which twotransformers are included as well as an installation according to theinvention,

[0006]FIG. 2 is an enlarged, schematic illustration of a heat pumpincluded in the installation according to the invention, and

[0007]FIG. 3 is an enlarged, schematic detail A in FIG. 1.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

[0008] In FIG. 1, numeral 1 generally designates a house in which twotransformers 2 are built-in. This house may consist of a small so-callednetwork station of the type that is installed adjacent to residentialdistricts or other houses with a limited size. The house 1 is divided ina number of compartments 3 by partition walls, which compartments areaccessed individually via openings recessed in outer walls of the house,which openings may be closed by means of shutters or doors 4. The twotransformers 2 are each installed in a compartment. In the othercompartments, other forms of auxiliary equipment for transformers areinstalled, e.g. disconnecting switchers, collector rails, etc. In one ofthese compartment, a heat pump in its entirety designated 5, included inan installation according to the invention, is mounted.

[0009] In each individual transformer 2, a schematically illustratedcooling device generally designated 6 is included. Said cooling devicemay consist of a vessel filled with oil in which the core and thewindings of the transformer are immersed. However, the cooling devicemay also be otherwise designed. The same may, for instance, consist of ahot air collecting space from which heat may be given off to anotherfluid than air via suitable heat exchangers.

[0010] Between the two transformers 2 and the heat pump 5, a first pipesystem 7 extends in which a first heat carrying fluid may be circulated,more precisely in a feeder pipe 7′ and a return pipe 7″. As is seen inFIG. 1, one of the ends of each one of said pipes is connected tocooling devices 6 of the transformers via branch ducts 8′, 8″. The otherend of each pipe 7′, 7″ is connected to a heat exchanger 9, e.g. a plateheat exchanger, placed near the heat pump 5. In practice, the pipesystem 7 may consist of single pipe lines, which are connected to theoil vessels of the transformer cooling devices via the existing nippleswhich conventionally are used for filling oil in the vessels. In otherwords, in this case the heat carrying fluid in the pipe system 7consists of the transformer's own cooling oil.

[0011] The above-mentioned pipe system 7 and the heat exchanger 9 havethe purpose of enabling emission of heat to an evaporator 10 included inthe heat pump 5, which evaporator in a known way via a second pipesystem 11 communicates with a compressor 12, a condenser 13 as well asan expansion valve 14. The pipe system 11 and the components 10, 12, 13,14 together form a closed pipe system in which a second fluid may becirculated in the usual way. Said second fluid consists of aconventional so-called cooling medium, e.g. of the type that containspropane, which can alternately be evaporated and condensed duringabsorption and emission, respectively, of heat.

[0012] A third pipe system 15, which includes a feeder pipe 15′ and areturn pipe 15″, is with one end thereof connected to the heat emittingcondenser 13 and with the opposite end thereof connected to one or moreheat consumption units 16. Said units may consist of, for instance,radiators or other heat emitting devices in buildings of differenttypes. The part of the pipe system 15, which is connected to thecondenser 13, is illustrated schematically in the form of a coil ofpiping 17 which is inserted in the interior of the condenser. Inpractice, the condenser consists, however, most suitable of a plate heatexchanger. In the feeder pipe 15′, there is a pump 18 by means of whicha heat carrying fluid, e.g. water or oil, can be circulated in the pipesystem 15.

[0013] Furthermore, in the installation according to the invention, afourth pipe system 19 is included, comprising two pipes 19′, 19″ whichalternately may serve as a feeder pipe and a return pipe, respectively,depending on the functional state of the installation. Said pipe systemis at least partly brought down in, for instance, rock, ground, or waterin the form of a lake or a sea, the environment around the undergroundor submarine part of the pipe system—depending on the installation'sfunctional state—serving either as a heat emitter (in the same way as inconventional so-called rock heat) or as a heat sink or accumulator. InFIG. 2, said combined heat accumulator and emitter, respectively, isschematically shown at 20.

[0014] In the shown embodiment, in which the first pipe system 7 isconnected to a heat exchanger 9, the fourth pipe system 19 is connectedto and integrated with a fifth pipe system 21 including first and secondpipes 21′, 21″ outside the evaporator 10. The connection of the pipesystem 21 to the evaporator is shown schematically in the form of awinding of piping 22, but also in this case, the evaporator consists ofa plate heat exchanger. In a branch point between homologous pipes, inthis case the pipes 19′ and 21′, in the two pipe systems 19, 21, amulti-port valve 23 is arranged of the type which not only may open andclose but also throttle the flows in the respective pipes. In the pipesystem 21, more precisely in the pipe 21′ between the multi-port valve23 and the evaporator 10, a pump 24 is arranged. The two pipe systems 19and 21 are integrated with each other so far that they contain one andthe same fluid, preferably in the form of a so-called Brine liquidwhich, for instance, may consist of a mixture of spirit and water.

[0015] Adjustment of the multi-port valve 23 is carried out by means ofa motor 25 which is driven electrically via an electric circuitschematically outlined with dash-dotted lines, in which a temperaturesensor 26 in the feeder pipe 7′ of the first pipe system 7 is alsoincluded. In this connection, it should also be pointed out that a pump27 to circulate the heat carrying fluid in the pipe system 7 is includedin the return pipe 7″ of the pipe system 7.

[0016] In the preferred embodiment shown in the drawing of theinstallation according to the invention, a particular heat indicator 28is connected to the heat consumption pipe system 15, e.g. a radiatorco-operating with a fan, which radiator is located in, for instance, thecompartment 3 in which the heat pump 5 is located. In all events, theheat indicator 28 should, however, be located inside the house. The heatindicator 28 is connected to the pipe system 15 via a sixth pipe system29. More precisely, a feeder pipe in this pipe system is connected tothe corresponding feeder pipe 15′ in the system 15 via a multi-portvalve 30, which is adjusted by a motor 31. A certain part of the heatenergy which is transported to the consumption unit 16 may, if required,be drawn off via the pipe system 29 and the heat indicator 28 with thepurpose of heating the air in the interior of the house 1, particularlythe air in the compartments 3 which are spaced-apart from thecompartments for the transformers 2.

[0017] The Function and the Advantages of the Installation According tothe Invention

[0018] Suppose that the installation is to work during the cold periodsof the year and that the conventional so-called rock heat function ofthe heat pump 5 is turned on. In this state, the multi-port valve 23keeps not only the feeder pipe 19′ from the underground heat emitter 20open, but also the part of the pipe 21′ that extends between the valveand heat exchanger 9. This means that fluid (Brine-liquid) having acomparatively moderate temperature (e.g. about 0° C.) is mixed withwarmer fluid from the heat exchanger 9, which in turn absorbs heatdirectly from the cooling devices 6 of the transformers 2 via the fluidcirculating in the pipe system 7. Therefore, the liquid that is mixed inthe multi-port valve 23 and then passes the evaporator 10 will have aconsiderably higher temperature than the liquid which is taken up fromthe underground via the feeder pipe 19′. Depending on varyingtemperatures in the underground as well as the cooling devices 6 of thetransformers, the temperature varies, of course, in the evaporator 10,but in practice it may very well be within the range of +10 to +15° C.By the fact that the temperature of the fluid circulating through theevaporator may be considerably increased (in average from about 0° C. to+10° C.) the efficiency of the heat pump is radically improved, moreprecisely from a factor 3 (in the normal case) to a factor 5-7 orgreater.

[0019] During the warm periods of the year, when the need for heating inbuildings is low or non-existent, the heat pump may need to temporarilybe put out of operation. Then, in order to still enable efficientcooling of the transformers, the multi-port valve 23 may be readjustedso that heat from the heat exchanger 9 is not utilized, per se, in theheat exchanger, but is led down into the underground (or to thesubmarine environment of the pipe system 19). This takes place byletting the pump 24 feed down the fluid in the pipe system 19 via thepipe 19′, which then acts as a feeder pipe, and then is brought inreturn to the pipe system 21 via the pipe 19″.

[0020] The advantages of the invention are obvious. When the need forheat to the consumption units during the cold season is high, surplusheat from the transformers 2 may be utilized for heating purposes in avery economic way at the same time as the cooling of the transformersbecomes efficient. During the warm season, when the need for heatingceases, the installation may, by adjustment of the valve 23, simply bereadjusted so that surplus heat from the transformers is led downunderground or submarine, the heat energy being stored in the rock orthe earth. The unit 20 then works as a heat accumulator from whichstored energy may be recovered during the cold season (when the pipesystem 19 is immersed in, e.g., sea or lake water, the water only servesas a heat sink). In other words, the installation according to theinvention guarantees efficient cooling of the transformer ortransformers in question irrespective of season, i.e. regardless if theheat pump needs to work for heating purposes or not.

[0021] Feasible Modifications of the Invention

[0022] The invention is not solely restricted to the embodimentdescribed above and shown in the drawings. Thus, it is feasible to sparethe particular heat exchanger between the first and fifth pipe systems,one and the same heat carrying fluid being circulated in the first,fourth and fifth pipe systems. As a heat carrying fluid in the pipesystem connected to the transformer, it is also feasible to use anotherliquid (or gas) than oil. Furthermore, it should be pointed out that theinstallation's heat pump according to the invention does not necessarilyhave to be mounted in the same house as the transformer or transformersin question. Thus, the heat pump may also be installed in or near thebuilding or the buildings to which the surplus heat energy from thetransformer is to be transferred for heating purposes. In such cases,the first pipe system extends more or less long-range between thetransformer house and the building or buildings in question. Neitherneed the above-mentioned consumption units to be installed indoors.Thus, the units may be placed outdoors (even underground) to simply emitheat energy. The installation then only serves to efficiently cool thetransformer.

1. Installation to utilize surplus heat from a power transformer (2) ofthe type that includes a cooling device (6) for cooling the windings ofthe transformer, characterized in that a first pipe system (7) isconnected to the cooling device (6) of the transformer for circulationof a first, heat carrying fluid between the cooling device of thetransformer and a heat pump (5) with the purpose of enabling emission ofheat to an evaporator (10) included in the heat pump, which in a knownway via a second pipe system (11) containing a second heat carryingfluid communicates with a compressor (12), a condenser (13) and anexpansion valve (14), that a third pipe system (15) having a third heatcarrying fluid for transfer of heat to one or more consumption units(16) is connected to the condenser (13) of the heat pump, that a fourthpipe system (19) is directly or indirectly connected to the first pipesystem (7), which fourth pipe system is partly brought down in a heataccumulator or emitter (20) in a rock, ground and/or water, and that amulti-port valve (23) acts between the first and fourth pipe systems (7,19) for leading surplus heat from the cooling device (6) of thetransformer via the first pipe system (7) to the evaporator (10) of theheat pump and/or to said heat accumulator (20).
 2. Installationaccording to claim 1, characterized in that the first pipe system (7) isconnected to a heat exchanger (9), which in turn is connected to theevaporator (10) of the heat pump (5) via a fifth pipe system (21), whichcommunicates with the fourth pipe system (19) and contains the same heatcarrying fluid as this, the multi-port valve (23) being arranged in abranch point between homologous pipes (19′, 21′) in said two pipesystems (19, 21).
 3. Installation according to claim 1 or 2,characterized in that the same is located in one and the same house (1)as the transformer (2) and that a heat indicator (28) is connected to afeeder pipe (15′) in the third pipe system (15) for heating the airinside the house.